Carcharhinidae - Requiem Sharks -- Discover Life

Carcharhinidae
REQUIEM SHARKS
Tiger sharks

REQUIEM SHARKS, BLUE SHARKS, LEMON SHARKS, SHARPNOSE SHARKS, TIGER SHARKS, WHITENOSE SHARKS, WHITETIP SHARKS

The requiems are one of the largest and best known family of sharks. Worldwide there are 50 species in 12 genera; 17 species in 7 genera occur in our region. They are active strong swimmers that occur singly or in small to large groups. They span a considerable range of sizes. For example, some milk sharks (genus Rhizoprionodon) reach a maximum length of less than 100cm, whereas the Tiger Shark (Galeocerdo cuvier) is among the largest of sharks with a maximum size of at least 7.4 m. Except for the Tiger Shark, which is ovoviviparous, all species are viviparous with a yolk sac placenta. They have litters of young that number from one or two to as many as 135. The pups resemble miniature versions of the adults and are able to fend for themselves moments after birth. Requiem sharks are responsible for about half of all reported shark attacks on humans. However, less than 100 attacks are reported each year worldwide and no more than 30 of these are fatal. Although attacks are extremely rare, the potential danger of the more aggressive species, such as the Tiger and Bull sharks, should be recognized. Spearfishermen are more prone to shark attack than other divers because fishes struggling on a spear emit low frequency vibrations which can attract sharks unerringly to the site. Once in the vicinity, the presence of blood, which is readily detected by the keen olfactory sense, adds to these sharks aggressive behavior. A few species have been shown to exhibit threat posturing involving exaggerated lateral swimming movements (i.e. arc of movement of the head increases noticeably), arching the back, holding the pectoral fins downward, and snapping of jaws. If these motions are evident, one should move slowly away from the shark and exit the water. They are voracious predators that feed mainly on a variety of fishes, other sharks, rays, squid, octopuses, cuttlefish, crabs, lobsters, and shrimps. Lesser items include sea birds, turtles, sea snakes, marine mammals, molluscs, and carrion, as well as human garbage.

Requiem sharks are characterized by having eyes with internal nictitating membranes; grooves along the side of the lips; teeth of variable sizes, with or without accessory points, upper and bottom teeth have different forms; 1st dorsal fin smaller than upper lobe of tail, situated before the pelvic fins; 2nd dorsal much smaller than 1st; lower lobe of tail well developed, upper lobe with undulating ridge along its top edge.